[1] The Aizu Domain was based at Tsuruga Castle in Mutsu Province, the core of the modern city of Aizuwakamatsu, located in the Tōhoku region of the island of Honshu.

In 1590, Toyotomi Hideyoshi awarded the Aizu Basin to Gamō Ujisato as part of a 919,000 koku fief following the submission of Date Masamune.

Ujisato was succeeded by his son, Gamō Hideyuki, but he fell out of favor with Hideyoshi and was transferred to Utsunomi with a reduction in his holdings to only 180,000 koku.

The Aizu Basin was then assigned to Uesugi Kagekatsu, who ordered by Hideyoshi to relocate from his power base in Echigo Province.

In 1600, after Tokugawa Ieyasu's victory at the Battle of Sekigahara, Uesugi Kagekatsu was deprived of his holdings in Aizu and was reassigned to the much smaller Yonezawa Domain in Dewa Province.

"In enemy territory, it is forbidden to rape women, harm the elderly and children, desecrate graves, torch the homes of commoners, slaughter livestock needlessly, pillage money and rice, cut trees without reason, and steal crops in the field.

Following Yoshinobu's resignation, Katamori took great pains to avoid conflict with the new Meiji government which could only be averted by an equitable settlement with the Tokugawa clan.

Although branded as an "enemy of the Court", Matsudaira Katamori was placed under house arrest and was later allowed to serve as the head kannushi for the Nikkō Tōshō-gū shrines to the Tokugawa clan.